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Studies show that both radio jets from the active galactic nuclei (AGNs) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain unclear. Here, we present an improved parametric model that allows us to statistically separate the SF and AGN components in observed quasar radio flux density distributions, and investigate how their relative contributions evolve with AGN bolometric luminosity (⁠|$L_\mathrm{bol}$|⁠) and redshift (z) using a fully Bayesian method. Based on the newest data from LOw-Frequency ARray Two-metre Sky Survey data release 2, our model gives robust fitting results out to |$z\sim 4$|⁠ , showing a quasar host galaxy SF rate (SFR) evolution that increases with bolometric luminosity and with redshift out to |$z\sim 4$|⁠. This differs from the global cosmic SFR density, perhaps due to the importance of galaxy mergers. The prevalence of radio AGN emissions increases with quasar luminosity, but has little dependence on redshift. Furthermore, our new methodology and large sample size allow us to subdivide our data set to investigate the role of other parameters. Specifically, in this paper, we explore quasar colour and demonstrate that the radio excess in red quasars is due to an enhancement in AGN-related emission, since the host galaxy SF contribution to the total radio emission is independent of quasar colour. We also find evidence that this radio enhancement occurs mostly in quasars with weak or intermediate radio power. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of the molecular gas properties of 17 Type 2 quasars at z < 0.2 from the Quasar Feedback Survey (L |$_{\rm [O~{\small III}]}$| > 1042.1  |$\rm ergs^{-1}$|⁠), selected by their high [O  iii ] luminosities and displaying a large diversity of radio jet properties, but dominated by LIRG-like galaxies. With these data, we are able to investigate the impact of AGN and AGN feedback mechanisms on the global molecular interstellar medium. Using Atacama Pathfinder EXperiment and ALMA ACA observations, we measure the total molecular gas content using the CO(1-0) emission and homogeneously sample the carbon monoxide (CO) spectral line energy distributions, observing CO transitions (J up  = 1, 2, 3, 6, 7). We observe high r 21 ratios (r 21  =  L 'CO(2-1)/ L 'CO(1-0)) with a median r 21  = 1.06, similar to local (U)LIRGs (with r 21 ∼ 1) and higher than normal star-forming galaxies (with r 21 ∼ 0.65). Despite the high r 21 values, for the seven targets with the required data, we find low excitation in CO(6-5) & CO(7-6) (r 61 and r 62 < 0.6 in all but one target), unlike high-redshift quasars in the literature, which are far more luminous and show higher line ratios. The ionized gas traced by [O  iii ] exhibits systematically higher velocities than the molecular gas traced by CO. We conclude that any effects of quasar feedback (e.g. via outflows and radio jets) do not have a significant instantaneous impact on the global molecular gas content and excitation and we suggest that it only occurs on more localized scales. [ABSTRACT FROM AUTHOR]

We present a study of molecular gas, traced via CO (3–2) from Atacama Large Millimeter/submillimeter Array data, of four z < 0.2, 'radio quiet', type 2 quasars (Lbol ∼ 1045.3–1046.2 erg s−1; L |$_{\mathrm{1.4\, GHz}}\sim 10^{23.7}\!-\!10^{24.3}$|   W  Hz−1). Targets were selected to have extended radio lobes (≥ 10 kpc), and compact, moderate-power jets (1–10 kpc; P jet ∼ 1043.2–1043.7 erg s−1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (V out = 250–440 km s−1) and spatial scales (0.6–1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9–53  per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly 'radio loud', brightest cluster galaxies. They have the following: projected distances of 5–13 kpc; bulk velocities of 100–340 km s−1; velocity dispersion of 30–130 km s−1; inferred mass outflow rates of 4–20 M⊙ yr−1; and estimated kinetic powers of 1040.3–1041.7 erg s−1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet–cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation. [ABSTRACT FROM AUTHOR]

When sustained for megayears (refs.  1,2 ), high-power jets from supermassive black holes (SMBHs) become the largest galaxy-made structures in the Universe 3 . By pumping electrons, atomic nuclei and magnetic fields into the intergalactic medium (IGM), these energetic flows affect the distribution of matter and magnetism in the cosmic web 4-6 and could have a sweeping cosmological influence if they reached far at early epochs. For the past 50 years, the known size range of black hole jet pairs ended at 4.6-5.0 Mpc (refs.  7-9 ), or 20-30% of a cosmic void radius in the Local Universe 10 . An observational lack of longer jets, as well as theoretical results 11 , thus suggested a growth limit at about 5 Mpc (ref.  12 ). Here we report observations of a radio structure spanning about 7 Mpc, or roughly 66% of a coeval cosmic void radius, apparently generated by a black hole between 4.4 - 0.7 + 0.2 and 6.3 Gyr after the Big Bang. The structure consists of a northern lobe, a northern jet, a core, a southern jet with an inner hotspot and a southern outer hotspot with a backflow. This system demonstrates that jets can avoid destruction by magnetohydrodynamical instabilities over cosmological distances, even at epochs when the Universe was 7 to 1 5 - 2 + 6 times denser than it is today. How jets can retain such long-lived coherence is unknown at present., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)